What is wrong with my leg muscle?

I was in swim practice yesterday and I randomly had a horrible pain in my calf muscle It felt horrible like my muscle was throbbing trying to move. I really felt like I was going to die haha. I've never felt anything so painful. My coach made it less painful by making me stretch and rubbing it but that still hurt. But it wasn't moving. He and many others said it was a cramp but I've felt a cramp before and that was nothing like a cramp. Cramps hurt but aren't so unbearable you want to cry. I did tear up. And today it still hurts. I have to walk in certain positions to keep it from aching but when I touch it, flex my toes, or put too much weight on my leg it hurts really badly. I don't think cramps last that long. I don't know what to do, I don't want to miss practice again. I didn't go today but my excuse was that I had an AP meeting which a lot of people were going to. But I really don't want to miss practice but I won't be able to handle the pain I don't want to tell my coach because I don't want him to think I'm over exaggerating because when he helped me he acted like it was an everyday thing. My friend said I should get it wrapped but I have a meet on Wednesday and I don't want him to leave me out.